This disclosure relates generally to methods for removing photoreceptor coatings from a substrate, wherein the photoreceptor coatings disposed over a substrate of an electrophotographic photoreceptor. More specifically, described herein are a photoreceptor coatings removal method which is based on an electrophotographic photoreceptor comprising a gelatin release layer between the photoreceptor substrate and one or more coating layers. The present embodiments provide a simple yet efficient method to reclaim and recycle the substrates for use in remanufacturing electrophotographic photoreceptors.
In electrophotography, the substrate for photoreceptors in a rigid drum format is required to be manufactured with high dimensional accuracy in terms of straightness and roundness, optimum surface reflectance and roughness, and desired thickness. In order to obtain such a dimensional accuracy, the substrate surface is polished at a high accuracy by using sand blustering, glass bean honing, or a diamond tool and/or the like. Once the substrate surface is formed, at least one coating of photosensitive material is applied to the substrate, which may comprise a charge generation layer and a charge transport layer, or their blended in a single layer, to form a full photoreceptor device.
Current drum photoreceptor may be commonly comprised of a rigid aluminum substrate having specific dimensions required for straightness, roundness and counter bore concentricity. For example, the wall needs to be minimized for efficient raw material cost but also thick enough to meet the one time machining requirements and physical requirements of the finished photoreceptor device. A defect-free surface with maximum reflectivity is provided by diamond machining to a mirror finish followed by glass bead honing. A maximum surface roughness is also specified. Preparation of the aluminum substrate surface is important in maintaining uniform, defect-free print quality. Minimizing the reflectivity of the surface, eliminates a defect causes by surface reflections that has the appearance of a plywood patterns in half tone areas of prints. Exceeding the maximum surface roughness leads to charge injection and high background.
The final product generally comprises three organic coatings, an undercoat layer (UCL), that functions as a primer, a charge generation and a charge transport, and in some cases, an anti-reflective coating and a hole blocking layer may also be included and applied directly over the substrate. The final assembly of the photoreceptor has two end caps (or flanges). One end cap comprises a drive gear and the other end cap comprises of a bearing and ground strap that has a spring contact to the bearing shaft and a friction contact to the inner substrate surface. The end caps are held in place with an epoxy adhesive and must meet a specified torque and push out force after a specified thermal cycle test condition.
The fabricated photoreceptor devices are expected to have good electrical and mechanical performance in a copier or printer. But, due to complexity of the manufacturing process, it is unavoidable to have varieties of defects in some photoreceptor devices which may meet the quality requirements for the copier or printer. The defective devices have to be rejected. In another aspect, each photoreceptive device has limited application life. Once the photoreceptor device cannot function well in the machine, it is also the end of the application life of the device. These used photoreceptor devices were usually disposed in the same way as the defective devices were treated. Disposal of the device could be very costly and could cause lots of environmental issues.
Remanufacturing such a photoreceptor device is difficult because the device dimensions are very specific and minor changes can adversely impact the results. For example, there is a specific balance between the substrate surface reflectance and surface roughness that must be maintained. Moreover, such photoreceptors have wall thicknesses that are too thin to re-machine, the coating layers comprise polymers that are chemically resistant to all but the most aggressive, and often non-environmentally friendly, solvents.
Currently used coating processes are only capable of coating aluminum substrates without flanges. In the case of end of line manufacturing rejects (5 to 15%), most rejected photoreceptors are coating rejects and are not flanged. However, field returns require flange removal before remanufacturing so that re-coating can be facilitated by the existing manufacturing process and also to ensure that the flanges would not be too worn out to meet the dimensional requirements of a new or re-manufactured photoreceptor. Flange removal without causing substrate deformation is necessary, but with complete adhesive residue removal, it is also important for maintaining the overall straightness, roundness and concentricity of the final re-manufactured assembly but difficult to achieve with the presently used processes.
Thus, there exists a need for methods to recycle or reclaim electrophotographic photoreceptor devices that would address the above-identified problems. Furthermore, there is a need to reduce the cost of remanufacturing electrophotographic photoreceptors, for example, by recycling the non-usable photoreceptor devices, through removing the photosensitive or coating layers without damaging the substrate formation. This would not only reduce the cost of producing the photoreceptor, but also decreases the cost for disposing all related materials in the devices.
Conventional photoreceptors and their materials are disclosed in Katayama et al., U.S. Pat. No. 5,489,496; Yashiki, U.S. Pat. No. 4,579,801; Yashiki, U.S. Pat. No. 4,518,669; Seki et al., U.S. Pat. No. 4,775,605; Kawahara, U.S. Pat. No. 5,656,407; Markovics et al., U.S. Pat. No. 5,641,599; Monbatiu et al., U.S. Pat. No. 5,344,734; Terrell et al., U.S. Pat. No. 5,721,080; and Yoshihara, U.S. Pat. No. 5,017,449, which are herein all incorporated by reference.
More recent photoreceptors are disclosed in Fuller et al., U.S. Pat. No. 6,200,716; Maty et al., U.S. Pat. No. 6,180,309; and Dinh et al., U.S. Pat. No. 6,207,334, which are all herein incorporated by reference.
The terms used to describe the imaging members, their layers and respective compositions, may each be used interchangeably with alternative phrases known to those of skill in the art. The terms used herein are intended to cover all such alternative phrases.